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Posts: 2 | Thanked: 0 times | Joined on Jan 2013
#1
Another broken N900 usb port, reporting in.

So, in the process of removing the stupid RF shielding from the board (it was in the way for my soldering iron), I accidentally knackered the component V5301 - the ESD protection circuit with my needlenose pliers.

Pictures:


(Data- pad was already lifted when I disassembled the unit).

I went back to the N900 schematic and found out that the ESD circuit was 'vampire-tapped' into the TX/RX lines on the USB. A few beers and then some brainstorming, I had the idea of hobbling together a similar circuit using tiny SMD components, and connect them back to the motherboard - not exactly back to the PCB, but hanging around, connected with some REALLY thin electrical wire I got from work.

Then I went to some of the posts under 'Broken mUSB idea: Creating a new connection', and found out that I could probably use the debugging(?) pads on the board as an alternate entry point.

I am curious as to whether my hypothetical solution will work, and if it will have any adverse effects such as USB to PC connections and battery charging (my hopes run high on this one, as the VBUS connection is intact), as well as if my improvised ESD protection -will- actually mitigate ESD at an acceptable level.

Here is the circuit, per V5301 layout on the RX-51 schematic




I plan on getting some of the required components (ESD protection diode, zener diode) from Mouser, list:

Diode: Toshiba df2b6.8m1act
Zener diode: Vishay Semiconductors SMF5V0A-GS08

If you have any better suggestions, go ahead and tell me.
(If it ain't gonna fit into the case - I'll dremel a hole in the casing to make some space for it).
 
Posts: 3 | Thanked: 1 time | Joined on Dec 2012
#2
I am a first grade Elektronic Engineering student, so I might be able to help. Unfortunately I dont know anything about the N900's schematic. Where can I find the schematic?
 
Posts: 2 | Thanked: 0 times | Joined on Jan 2013
#3
Originally Posted by RRvW View Post
I am a first grade Elektronic Engineering student, so I might be able to help. Unfortunately I dont know anything about the N900's schematic. Where can I find the schematic?
http://bit.ly/WfZicG

Look for V5301, page 4.

I intend to piggyback the improvised ESD protection circuit onto the debugging pads.
 
Posts: 767 | Thanked: 940 times | Joined on Jan 2011 @ Touring
#4
Following this thread, I did the exact same thing with my first N900.
I have a bricked in a week Hong Kong "new" N900 that I might be able to steal the part off of.
 
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